Flash bulb

ABSTRACT

A flash bulb of the combustible type in which at least the current conductors within the envelope are surrounded by a separate tubular body which shields the envelope walls from heat and ignition and shields the current conductors from the wire filling.

United States Patent [1 1 Van Der Tas et al.

1 1] 3,768,957 1 OCL- 30, 1973 FLASH BULB Inventors: Johannes Cornelis Van Der Tas;

Charles Cornelis Eduard Meulemans, both of Emmasingel, Eindhoven, Netherlands U. S. Philips Corporation, New York, NY.

Filed: Sept. 21, 1971 Appl. No.: 182,551

Related US. Application Data Continuation of Ser. No. 860,914, Sept. 25, 1969, abandoned.

Assignee:

U.S. Cl. 431/95 Int. Cl. F21k 5/02 Field of Search .L ..431/93-9 5 Primary Examiner-Carroll B. Dority, Jr.

Attorney-Frank R. Trifari 5 7 ABSTRACT A flash bulb of the combustible type in which at least the current conductors within the envelope are surrounded by a separate tubular body which shields the envelope walls from heat and ignition and shields the current conductors from the wire filling.

3 Claims, 3 Drawing Figures Chm-5m PATENTEDncI 30 m5 INVENTORS JOHANNES C.VAN DER TAS CHARLES C.E.MEULEMANS BY AGEN FLASH BULB This is a continuation of US. Pat. application Ser. No. 860,914, filed Sept. 25, 1969.

The invention relates to a flash bulb of the combustible type having an envelope of transparent material which includes an oxidizable metal, an oxidizing gas and a mass which can be ignited electrically, to which end current conductors are provided which terminate in the ignition mass within the envelope and are passed to the exterior through the lamp cap. 7

in the conventional flash bulbs of the combustible type the envelope consists of glass and has a bright or blue-coloured lacquer coating. The envelope contains oxygen and a zirconium wire filling. Furthermore an ignition device is present, which may comprise two current conductors interconnected by a filament within the envelope. Provided on the filament or on the terminals of the current conductors is an ignition mass which usually consists of a mixture of zirconium powder, potassium percheorate and a binding agent. The current conductors are generally fixed relative to each other in the lamp by means of a body or bead of electrically insulating material. A lamp provided with an ignition device of this nature may be ignited by means of a source of low voltage.

In a flash bulb of the combustible type for ignition by means of a source of high voltage, the filament is absent in the ignition device. The ignition mass is then provided, for example, on the bead. Ignitiontakes place by breakdown through the ignition mass followed by passage of current, the heat required to initiate the explosive combustion being produced in the ignition mass.

According to the invention anumber of advantages are obtained with a combustible type flash bulb which is characterized in that its envelope includes a tubular body having a longitudinal axis which is substantially parallel to the longitudinal axis of the envelope, and which body surrounds at least the current conductors. In a typical arrangement of the ignition device the longitudinal axis of the tubular body will coincide or substantially coincide with the longitudinal axis of the envelope.

The use of a tubular body according to the invention provides a solution to a number of problems which may occur in flash bulbs suitable for ignition with the aid of source of low voltage and in flash bulbs suitable for ignition with the aid of a source of high voltage. A tubular body which surrounds the current conductors in the envelope prevents parts of the oxidizable metal, which may be present in the envelope from causing short circuit between the current conductors, a example of the oxidizable metal being as a wire filling of metal fibres having a length of approximately 10 cm and a section of approximately pm X pm. A short circuit of this nature is a particular drawback in a flash bulb designed for ignition with the aid of a source of high voltage because the result of such a short circuit may be that breakdown of the ignition mass does not occur when applying the high voltage.

Still further advantages are obtained if the length of the tubular body is chosen to be such that the ignition mass is provided within the tube. Incandescent particles are hurled away during the explosive combustion of the ignition mass. The largest concentration of oxidizable metal (for example metal wire filling) is usually found between the ignition mass and the end of the lamp remote from the lamp cap; The risk of incandescent particles of the explosively burning ignition mass striking the wall of the envelope is notimaginary under these circumstances, and the particles hurled onto the I wall of the envelope cause loss of light due to absorption. 1

In some cases the explosive combustion is accompanied by a shock wave, and the combined action of all this may result in the wall of the envelope being weakened and possibly collapsing locally. This is particularly the case if the distance between the ignition mass and the wall of the envelope is small, for example, in the order of 1 mm, and the ratio between the length and the diameter of the envelope is large, such as in a needle-like flash bulb.

However, if the ignition mass is provided within the tubular body, the incandescent particles can only emerge from the tubular body into the direction where the larges concentration of metal to be turned is provided in the lamp. The risk of incandescent particles striking the wall of the envelope is effectively reduced while a shock wave occurring in a plane through the ignition mass and at right angles to the longitudinal axis of the envelope is taken up by the tubular body. All this has no noticeableinfluence on the speedat which the flash bulbs according to the invention are ignited.

The construction-in question still provides another advantage. When parts of the metal'wire filling approach the ignition mass in flash bulbs closely, the applied high voltage may leak away. This may result in the ignition not taking place or not taking place satisfactorily, and the risk of such an occurrence isreduced-by the construction according to the invention. In a flash bulb suitable for ignition by means of a source of low voltage, the leakage of heat generated in the filament towards the metal wire filling is prevented. if in such a lamp, a heat contact across part of a metal wire filling exists between the metal wire filling and the filament,

the ignition may fail.

It has been found in practice that for obtaining the said advantages, it is favourable when the distance between the .end face of the tubular body and the ignition mass is at least equal to the internal diameter of the tubular body, and is at least equal to the smallest diameter if the section is not circular.

The tubular body consists preferably of an electrically non-conducting material which is inert to the filler gas. A technologically interesting material having these properties is glass; The thickness of the wall of the tubular body may be, for example, 0.5 mm. with a suitable internal diameter of 2 to 5. mm. The cross section of the tubular body may be circular, or elliptic or may have approximately the same shape as the section of a possibly present bead for fixing the current conductors.

The tubular body may be placed in the lamp prior to or after the lamp cap with sealed current conductors has been formed. In the first case it is possible to form one assembly of the tubular body and the lamp cap with the tubular body sealed within the lamp cap during the manufacture thereof.

The ignition mass consists in principle'of a mixture of a metal powder, an oxidizing agent and a binding agent. In an ignition voltage for high voltage ignition, a semiconducting material may additionally be present.

In order that the invention may be'readily carried intoeffect, a few embodiments thereof willnow be described in detail, by way of example with reference to FIG. 1 is a cross-sectional view of a flash bulb of the combustible type for ignition by means of low voltage, cut by a plane parallel to the central axis of the lamp cap.

FIG. 2 shows the same sectional view through a combustible type flash bulb for ignition by means of high voltage.

FIG. 3 is a sectional view of a combustible type flash bulb for ignition by means of low voltage taken at right angles to the plane of the lamp cap.

In FIG. 1, the flash bulb for ignition by means of low voltage comprises a glass envelope or bulb part 1 containing a metal wire filling 2. Two current conductor wires 3 and 4 are provided which are sealed to the lamp cap 5 or base part, the wires 3 and 4 being fixed relative to each other in the lamp by means of a bead 6. The current conductor wires 3 and 4 are electrically connected together by means of a filament 7 on which the ignition mass 8 is provided, and tubular body 9 surrounds the current conductor wires 3 and 4, which body extends from the lamp cap up to above the ignition mass.

The tubular body 9 prevents parts of the metal wire filling 2(a) from shortcircuiting the current conductor wires 3 and 4(b), or from establishing heat-exchanging contact with the filament 7, and this body reduces the risk of incandescent parts of the explosively burning ignition mass 8 from touching the wall of the envelope 1 during the explosive combustion.

In FIG. 2 the reference numerals have the same significance as those in FIG. 1. Since the flash bulb is intended for ignition by means of high voltage, the filament 7 which connects the ends of the current conductor wires 3 and 4 in the lamp of FIG. 1 is absent and the ignition mass 8 is provided within the tubular body 9. In an advantageous embodiment of the invention the distance between the end face of the tubular body 9 and the ignition mass 8 is approximately equal to the internal diameter of the tubular body 9. This body 9 prevents parts of the metal wire filling 2 from shortcircuiting the current conductor wires 3 and 4 and reduces the risk of parts of the metal wire filling 2 from approaching the ignition mass 8 so closely that leakage paths for the high voltage are brought about. In addition the tubular body 9 effectively. shields the wall of the envelope 1 from shock waves occurring and incandescent particles hurted away from the ignition mass.

In FIG. 3 is shown a flash bulb suitable for ignition by means of low voltage having reference numerals with the same significance as those in FIG. 1 and 2. The part of the tubular body 9 sealed in the lamp cap 5 is denoted by the reference numeral 10.

What is claimed is:

l. A flashlamp comprising a tubular, transparent envelope having a longitudinal axis, said envelope being closed at one end and secured to a base section at the other end, lead-in wires extending through said base section into said envelope, a bead of non-conductive material secured between said lead-in wires within said envelope, an ignition mass arranged in cooperative relationship with the ends of said lead-in wires positioned within said envelope, an oxidizable metal within said envelope, an oxidizing gas within said envelope, said ignition mass cooperating with said oxidizable metal and said oxidizing gas to produce intense actinic rays from said flashlamp, and a tubular non-combustible open ended shield secured at one end to said base section within said envelope, said shield having a longitudinal axis of said envelope and generally continuous walls surrounding said ignition mass between said ignition massand said envelope for preventing said ignition mass from spreading burning particles in directions perpendicular to the longitudinal axis of said envelope that can strike and break the envelope, said oxidation metal being located between said envelope and said shield.

2. A flashlamp as claimed in claim 1 wherein said tubular non-combustible shield surrounding said ignition mass shields said ignition mass for a distance at least equal to the internal diameter of said tubular noncombustible shield.

3. A flashlamp as claimed in claim 1 wherein said tubular non-combustible shield comprises glass.

mg UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No. 37 68957 Dated October 30, 1973 Inventor(s) JOHANNES CORNELIS VAN DER I'AS ET. AL.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Insert after ['21] Appl. No.: 182,551, --Fereiign Afiplication Priority Data, September 27,- 1968,

Netherlands 6813920 1 Column 1, line 51, "a" should be -anline 65, after "example" insert --the- Signed and. sealed this 21st day of Ma; 19724..

(SEAL) Attest:

} EDWARD I-I.I-="Li1ZTCZIi3R,JR. C. MARSHALL DAMN Attesting Officer Commissionerof Patents 

1. A flashlamp comprising a tubular, transparent envelope having a longitudinal axis, said envelope being closed at one end and secured to a base section at the other end, lead-in wires extending through said base section into said envelope, a bead of non-conductive material secured between said lead-in wires within said envelope, an ignition mass arranged in cooperative relationship with the ends of said lead-in wires positioned within said envelope, an oxidizable metal within said envelope, an oxidizing gas within said envelope, said ignition mass cooperating with said oxidizable metal and said oxidizing gas to produce intense actinic rays from said flashlamp, and a tubular non-combustible open ended shield secured at one end to said base section within said envelope, said shield having a longitudinal axis of said envelope and generally continuous walls surrounding said ignition mass between said ignition mass and said envelope for preventing said ignition mass from spreading burning particles in directions perpendicular to the longitudinal axis of said envelope that can strike and break the envelope, said oxidation metal being located between said envelope and said shield.
 2. A flashlamp as claimed in claim 1 wherein said tubular non-combustible shield surrounding said ignition mass shields said ignition mass for a distance at least equal to the internal diameter of said tUbular non-combustible shield.
 3. A flashlamp as claimed in claim 1 wherein said tubular non-combustible shield comprises glass. 